The present invention relates to gas turbine engines, and, more specifically, to the deicing therein.
During flight and/or while grounded, aircraft may encounter atmospheric conditions that cause the formation of ice on airfoils and other surfaces of the aircraft. If accumulating ice is not removed, it can change the aerodynamic profiles of the components being iced, adversely affecting the aerodynamic performance of the engine. Hence, aircraft engines are required to demonstrate the ability to operate in an icing environment to show compliance with Federal Aviation Administration requirements.
Ice accumulation has conventionally been accommodated by configuring affected compressor airfoils with an increase in ruggedness to avoid or minimize problems caused by ice liberation. Commercial engines have been able to alleviate operability issues caused by ice accumulation by raising flight idle or ground idle speeds without violating thrust constraints. However, as technology drives commercial engines to achieve higher and higher bypass ratios, some of the operability issues are becoming more severe than encountered in the past, since more engine airflow will correspondingly increase the amount of ice accumulation which must be accommodated.
Furthermore, ever larger fan blades that operate at slower rotational speeds are being designed with state of the art composite materials. Slow fan speeds can permit more accumulation of ice in certain icing conditions.
One way of reducing the ice accumulation on booster airfoils is to provide heat to the inlet guide vanes (IGVs), as is disclosed in commonly assigned, co-pending U.S. application Ser. No. 09/932595. Hot air from the high pressure compressor could be allowed to flow through hollow IGVs. However, hollow IGVs tend to have an increased thickness. While the anti-ice system of such a configuration works well, there can be some performance loss with the thicker, hollow IGVs.
An alternative to circulating air through the inlet guide vanes is to use compressor bleed air channeled through the manifold and out the splitter nose for de-icing, as was also disclosed in commonly assigned, co-pending U.S. application Ser. No. 09/932595. However, the amount of bleed compressor air used to de-ice the booster splitter leading edge is considered to be a heretofore necessary performance loss to the engine cycle. This loss is a result of the work done to the ambient air by the compressor to pressurize it and thereby melt ice off the splitter nose, which work is not then used by the turbomachinery components to produce thrust.
It would be desirable, therefore, to provide an anti-icing technique that effectively reduces ice threat to aircraft without increasing aerodynamic total pressure losses due to the increased thickness of hollow IGVs.
The present invention reduces ice threat to the internal surfaces of aircraft engines, eliminating both the need for hollow inlet guide vanes and/or the use of an internal heavy and complex piping system to deice the booster splitter leading edge surfaces. The present invention has the additional advantage of eliminating the need to use compressor air, with the associated performance penalty of such air use, and bulky valves with their added system weight. The present invention uses electric coils meshed into the booster splitter lip near the leading edge in a conventional turbofan engine, to reduce ice accumulation on surfaces internal to the engine.
Accordingly, the present invention provides a system and method for preventing the formation of ice on or removing ice from an internal surface of an aircraft engine.